Art of converting phosphorites.



" percentage of heating operation as barren snares PATENT OFFICE.

HENRY VAIL DUNI-IA'M, 0F BAINBRIDGE, YORK, ASSIGNOR TO NACIREMA CHEMICALCOMPANY, A CORPORATION OF VERMONT.

' ART OF CONVERTING PHOSPHORITES.

Specification of Letters Patent. Application filed September 14, 1911.Serial No. 649,326.

Patented Oct. a, rats.

Be it known that I, HENRY V. DUNHAM, a citizen of the United States,residing at Bainbridge, in the county of Chenango and State of New York,have invented or discovered certain new and useful Improvements in theArt of Converting Phosphorites, of which the following is aspecifiestion.

phosphorites or phosphate rock to render the same suitable forfertilizing purposes, and has for its object so to treat the phosphaterock, by a relatively inexpensive process, that the treated product willcontain a large citrate soluble or dilute citric acid soluble phosphate,which is suitable for plant life and which is known in the art asavailable phosphate, or available phosphoric acid. Y The present processof rendering the phosphoric acid in the rock available for use, whichprocess is applicable to phosphorites whether they be in the form ofphosphates of. calcium, iron or aluminum, consists broadly in mixingwit-h the said phosphorites, reagents which are decomposed by heatingand which evolve certain gases when heated to the decomposing points.The gases produced -may be a mixture of carbon dioxid and either sulfurdioxid or sulfuric anhydrid; the essential requirements for producingthe desired reactions being that. the carbon dioxid and sulfur dioxid ortrioxid must be used while in the nascent'condition, which isaccomplished by having the reagents from which they are produced inastate of intimate association with the finely ground phosphate rock.

In carrying this invention into effect the phosphate rock is firstground to about 80 or 100 mesh. To the ground'phosphorite is then addedrelatively small proportions of any desired carbonate (unless thegroundphosphate contain a carbonate) and of any desired sulfate or otherequivalent reagent, and preferably an amount of Water sufiicient to forma thin mud when the water and reagent have been well mixed with theground rock or phosphorite. The mixture 18 then heated, without theaddition of other materials thereto, in a calcining furnace to a highheat, preferablya white heat, the mix-v ture being agitated throughoutthe whole for instance by employ- This invention relates to thetreatment of mg a rotary cylindrical calciner and rotatmg the samecontinuously. This heating treatment is continued for about one hour,the length of time of the heating treatment depending somewhat upon thequality. or grade of rock being treated.

I find that to cause the conversion of every 100 lbs. of phosphate rocksuitable proportions of reagent are 12 lbs. of sodium sulfate and 12lbs. ofcalcium or sodium carbonate. The mixture of nascent carbon dioxidand sulful dioxid or sulfuric anhydrid produced by heating reacts on theground phosphate and. converts it into avallable phosphate, which is notsoluble in water, but is soluble in ammonium citrate solution.

In carr ing' out my process no carbon, coal, or 1i (e .reducing agent isadded to the mixture of phosphate rock, and converting salts. Theaddition of such reducing agents would prevent the formation of materialamount of carbon dioxid, sulfur dioxid and sulfur trioxid.

After the heated phosphate rock has been properly calcined it is removedfrom the furnace, and when it has cooled it is ground to a fine powderof from 80 to 100 mesh. Itis then ready to be applied to the soil ormixed with other ingredients which are generally used in the manufactureof fertilizers.

. Having thus described my invention I claim and desire to secure byLetters, Patent:

1. A process of converting the phosphoricacid of phosphate rock into theammonium citrate-soluble state, but not into the watersoluble state,which comprises producing an intimate mixture of said phosphate, acarbonate and a sulfate, and heating said mixture to substantially awhite heat, in the substantial absence of reducin agent's, until saidconversion is substantiafiy complete.

2. A process of rendering the phosphoric acid of phosphate rock solubleinammonium citrate'solution, but not soluble in water, which comprisesproducing an intimate mixture of said phosphate an alkali metalcarbonate and an alkali metal sulfate, and heating said. mixturetoawhite heat, in the substantial absence of reducing agents, until saidconversion is substantially complete.

3. A process of rendering the phosphoric acid of phosphate rock solublein ammonium citrate, but" not in water, said process comprising the stepof producing an intimate mixture of said phosphate, an alkali metalcarbonate and an alkali metal sulfate, each in amount equal to about 12%of the amountof phosphate rock, and heating said mixture tosubstantially a white heat, in the substantial absence of reducingagents, for about one hour.

4. A process of converting the phosphoric acid of phosphate rock into acondition in which it is soluble in ammonium citrate, but insoluble inwater, which comprises producing an intimate mixture of said phosphate,a carbonate and a sulfate, by mixing said materials in the presence ofsufficient water to form a plastic mass, and heating said mixture tosubstantially a white heat, in the substantial absence of reducingagents, until said conversion is substantially complete.

5. A process of converting the phosphoric acid of phosphate rock intocitrate-soluble, but not water-soluble condition which comprisesproducing an intimate mixture of said phosphate, a carbonate and asulfate, and

heating said mixture to substantially a white 6. A process of convertingthe phosphoric .acid of phosphate rock into a form in which it issoluble in neutral citrate solution, but insoluble in water, whichcomprises produc ing an intimate admixture of said phosphate, acarbonate and a sulfate, and heating said admixture to substantially aWhite heat, in the substantial absence of reducing agents, whilecontinuously agitating said mixture, until said conversion issubstantially complete. a I In testimony whereof I aflix my signature,in presence of two Witnesses.

HENRY VAIL DUNHAM. Witnesses:

A. A. DUNHAM, R. G. W1Lcox.

